Where do you store long-term memories?

There is no single 'store' in your brain for long-term memories. Instead, they are all over the cortex, in the brain areas which were active when you first experienced them. So for a complete memory (composed of sights, sounds, etc.) to be retrieved, all the different bits must be brought together. How this happens is still a mystery, but it may be co-ordinated by the hippocampus.